CO2 fixation by hydrogenation over coprecipitated Co/Al2O3

CO₂ fixation by hydrogenation over coprecipitated 36 wt.% Co/Al₂O₃ has been studied under a range of reaction conditions to clarify the effects of reaction variables and to determine the kinetics and mechanism of the reaction. A comparison of the results with those reported for CO hydrogenation on the same catalyst indicates that, although product distributions of CO₂ and CO hydrogenation differ, the kinetics and mechanism are similar.     

Incorporation of an allene unit into alpha-pinene: generation of the cyclic allene 2,7,7-trimethylbicyclo[4.1.1]octa-2,3-diene and its dimerization

The reaction of etheral methyllithium with 3,3-dibromo-2,7,7-trimethyl-tricyclo[4.1.1.0(2,4)]octane (2) was investigated. The generated carbene 12 undergoes intramolecular C-H insertion to provide the tetracyclic hydrocarbon 3 and the bicyclic allene 15, which undergoes [2+2] cyclodimerization. The structures of the formed allene dimers 16, 17, and 18 were elucidated by spectral means. The activation barriers for all possible C-H insertion products 3, 13, and 14 and the allene 15 were investigated by using density functional theory computations at the B3LYP/6-31G(d) level. It was found that the activation barriers for the formation of 3 and 15 (6.2 and 6.3 kcal mol(-1)) are much lower than that for the insertion products 13 and 14 (17.5 and 12.6 kcal mol(-1)), respectively. This prediction was completely in agreement with our experimental results.     

Fabrication of Co/CoO Exchange Bias System by Ion Implantation and Its Magnetic Properties

We use ion implantation as a new approach to build an anti-ferromagnetic （AFM） cluster embedded exchange bias （EB） system. Co film with thickness of 130nm is deposited on the Si （111） substrate using magnetron sputtering, 60keV O＋ is chosen to implanted into the Co film to form CoO AFM clusters coupling with Co matrix at the interface. By measuring the hysteresis loop after field-cooling, significant shifts of loop along the applied field are confirmed. When increasing the implantation dose to 2×1017/cm2 and annealed samples in N2 atmosphere, we obtain the highest HEB to 458Oe.     

Modulated Phase of a Potts Model with Competing Binary Interactions on a Cayley Tree

We study the phase diagram for Potts model on a Cayley tree with competing nearest-neighbor interactions J ₁, prolonged next-nearest-neighbor interactions J _p and one-level next-nearest-neighbor interactions J _o . Vannimenus proved that the phase diagram of Ising model with J _o =0 contains a modulated phase, as found for similar models on periodic lattices, but the multicritical Lifshitz point is at zero temperature. Later Mariz et al. generalized this result for Ising model with J _o ≠0 and recently Ganikhodjaev et al. proved similar result for the three-state Potts model with J _o =0. We consider Potts model with J _o ≠0 and show that for some values of J _o the multicritical Lifshitz point be at non-zero temperature. We also prove that as soon as the same-level interactionJ _o is nonzero, the paramagnetic phase found at high temperatures for J _o =0 disappears, while Ising model does not obtain such property. To perform this study, an iterative scheme similar to that appearing in real space renormalization group frameworks is established; it recovers, as particular case, previous work by Ganikhodjaev et al. for J _o =0. At vanishing temperature, the phase diagram is fully determined for all values and signs of J ₁,J _p and J _o . At finite temperatures several interesting features are exhibited for typical values of J _o /J ₁.     

Residual properties and almost equicontinuity

A propertyP of a compact dynamical system (X,f) is called a residual property if it is inherited by factors, almost one-to-one lifts and surjective inverse limits. Many transitivity properties are residual. Weak disjointness from all propertyP systems is a residual property providedP is a residual property stronger than transitivity. Here two systems are weakly disjoint when their product is transitive. Our main result says that for an almost equicontinuous system (X, f) with associated monothetic group Λ, (X, f) is weakly disjoint from allP systems iff the onlyP systems upon which Λ acts are trivial. We use this to prove that every monothetic group has an action which is weak mixing and topologically ergodic.     

pH值对水热合成磷酸铋的光催化性能的影响

利用水热法通过调节溶液的pH值合成了不同物相和形貌的磷酸铋.用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对样品进行了物相和形貌表征,并以10 mg·L-1的亚甲基蓝溶液为目标降解物,对材料的光催化降解性能进行了评价.结果表明:前驱物溶液的pH值对磷酸铋的形貌、物相和光催化性能都有较大影响.前驱物溶液pH值为1.3时制得的磷酸铋的光催化性能最高,室温汞灯照射20 min,亚甲基蓝的降解率可达到99.61;.     

利用卟啉中位羧基基团直接缩合卟啉二聚体

卟啉单体的直接偶合法. 这种方法包括有β-β, meso-β直接连接的二聚体[8,9]和直接连接的N混杂的卟啉二聚体[10]. 我们利用二环己烷基羰化二亚胺(DCC)作催化剂, 在冰盐浴条件下, 通过两个5-(p-羧基苯基)-10,15,20-三苯基卟啉(H2CPTPP)周边上的羧酸基团一步直接缩合获得以羧酸酐连接的新型卟啉二聚体. 利用多种光谱手段证实所合成的物质为目标产物. 该方法具有反应物单一、 反应步骤简单、 副反应少、 产物纯化方便、 时间短和产率高等优点.     

一种新型可光降解的PVC-OA-TiO_2纳米复合膜

采用包埋技术制备了一种新型可光降解的聚氯乙烯-草酸-TiO_2(PVC-OA-TiO_2)纳米复合膜,并研究了紫外光照射条件下该复合膜的光催化降解情况.结果表明,该纳米复合膜的光催化降解是一个氧化断链过程,经紫外光照射310 h后失重率达到55%,是PVC-TiO_2复合膜的2倍,是纯PVC膜的3.5倍,说明草酸的掺杂可以促进PVC-OA-TiO_2复合膜更快地被光降解.草酸作为一个良好的电子给体,能不可逆地与TiO_2表面产生的空穴或表面羟基反应,抑制电子和空穴的复合,从而显著提高PVC-OA-TiO_2的光催化降解速率.